1. Field of the Art
The present invention relates to a spicamycin derivative which has an antitumor activity and is useful for medicines and a salt thereof, an antitumor agent containing the compound and a method for inhibiting tumor by using the compound.
2. Related Art
Hitherto, the present inventors have found the spicamycin represented by the formula: ##STR5## wherein R.sub.3 represents (CH.sub.3).sub.2 CH(CH.sub.2).sub.n CO-- (n=8-14) or CH.sub.3 (CH.sub.2).sub.m CO-- (m=10-16) and R.sub.4 represents CH.sub.2 OHCH(OH)-- (see Japanese Patent Laid-Open Publication No. 161396/1984).
The present inventors have also found Spicamycin X having 12 carbon atoms at the fatty acid side chain as a spicamycin compound which has a lower toxicity and a higher therapeutic coefficient as well as a unified component so that the compound can be used clinically as an antitumor agent (see Patent Application No. PCT/JP90/00781).
Spicamycin has a structure in which a specific aminoheptose, referred to hereinafter as spicamine, is bonded to the amino group at the 6-position of the purine, glycine is bonded by amide bond to the amino group at the 4-position of the spicamine and a fatty acid is further bonded by amide bond to the amino group of the glycine.
As the compounds having a similar structure to spicamycin, septacidin which is an isomer at the 2'-position of spicamine (see U.S. Pat. Nos. 3,155,647 and 3,264,195) and analogues of septacidin [Antimicrobial Agents and Chemotherapy, 845-849 (1965)] are known. These compounds, however, exhibit no antitumor activity against L1210 mouse leukemia and Walker 256 rat sarcoma [see Journal of Medicinal Chemistry, 20 (11), 1362, (1977); Nucleoside Antibiotics, Wiley-Interscience, New York, N.Y., p. 256 (1970)] and thus have a narrow antitumor spectrum.
The well-known compounds described above have problems to be solved and thus are presently not used clinically.